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Tüberküloz ve Toraks Dergisi 2010; 58(2): 229-230 Gravimetric methods are simple and reliable for eva-luating the lung edema in ischemia reperfusion (IR) injury models (1). Wet to dry weight ratio (WDR) is the most frequently used gravimetric method in the literature. To determine WDR, the whole lung, lobes, or segments of peripheral lung are weighed after ini- tial removal and dried in an oven at a constant tem- perature for a period (1). This drying period is not clear and ranges from 24 hours to two weeks in the literature (1-3). Our purpose was to determine the optimal drying period for this method in IR induced rat lung edema model.
Six rats were control and other six underwent hind limb IR injury (one hour ischemia and two hour reperfusion was applied to the right hind limb by tourniquet met- hod) for constitution lung edema. After the lung remo- val, the right lungs were weighed wet, and then dried in an oven at 65°C, and weighed at 2, 4, 6, 12, 24thho- urs to 7thdays. WDR was calculated using following Formula; WDR = (wet-dry weight) x 100/dry weight.
Mann-Whitney U test was used for analysing the diffe- rence between two groups.
Rat weights were not different in between control and IR groups (295 ± 4 vs. 297 ± 4 g, p= 0.545, respecti- vely). In both groups, lungs lost %80 of their wet we- ight up to six hours and after that point, no weight loss was seen up to seven days (Table 1). Lung weights we- re significantly heavier in IR group than control at the all drying periods (p< 0.05).
The simplest way to evaluate edema formation in the lung is to use a gravimetric method. There are four me- asures commonly applied: lung wet weight, WDR, lung body weight index, and extravascular lung water. Yos- hikawa reported that, WDR had an excellent correlati- on with bronchoalveolar lavage fluid albumin and total protein during graded injury, high-airway pressure lung injury in mice (5).
Currently, we showed that, the lungs in both groups lost 80 percent of their total weight in the first six ho- urs, and this weight loss ceased after that point up to the 7thday. Therefore, in contrast to classical applica- tion, six hours drying period is good enough to measu- re wet to dry weight ratio, and no need for the longer.
Editöre mektup/Letter to the editor
Determination of optimal drying period in wet to dry weight ratio measurement
Ali YEĞİNSU, Makbule ERGİN
Gaziosmanpaşa Üniversitesi Tıp Fakültesi, Göğüs Cerrahisi Anabilim Dalı, Tokat.
Yazışma Adresi (Address for Correspondence):
Dr. Ali YEĞİNSU, Gaziosmanpaşa Üniversitesi Tıp Fakültesi, Göğüs Cerrahisi Anabilim Dalı, 60100 TOKAT-TURKEY
e-mail: yeginsu@hotmail.com
Determination of optimal drying period in wet to dry weight ratio measurement
230
Tüberküloz ve Toraks Dergisi 2010; 58(2): 229-230Edematous lung weights were heavier than those of controls in all drying periods. The source of this diffe- rence resulted from the water and solute substance as- sociated with water, such as protein, and its derivati- ves, accumulating in the lung tissue. During drying pe- riod, the water evaporates, but solute substances re- main in the alveolar space. Here, the point that should be emphasized is, whereas up to 6thhour, water is the major determinant of lung weight, as the drying period lenghtened, after 6th hour, alveolar solute materials replaced with water as the major determinant of the lung weight. Therefore, measurements after six hours drying period shows the accumulation of solute subs- tance in tissues.
In this study, we used a hind limb IR model to induce lung edema. This model is more practical than lung IR model. We used right lungs, because total lung block contains tissues other than lung, such as, trachea and mediastinal fat tissue, and the right lung constitutes 2/3 of total lung weight. We perfused the lungs with 20-25 cmH2O pressure, and perfusion was continued 2-3 minutes.
In conclusion, six hours drying period is good enogh to calculate WDR. No need for longer drying.
REFERENCES
1. Parker JC, Townsley MI. Evaluation of lung injury in rats and mice. Am J Physiol Lung Cell Mol Physiol 2004; 286:
231-46.
2. Yildiz G, Demiryurek AT, Gumusel B, Lippton H. Ische- mic preconditioning modulates ischemia-reperfusion in- jury in the rat lung: role of adenosine receptors. Eur J Pharmacol 2007; 556: 144-50.
3. Ishibe Y, Liu R, Ueda M, et al. Role of inhaled nitric oxide in ischaemia-reperfusion injury in the perfused rabbit lung. Br J Anaesth 1999; 83: 430-5.
4. Balci EA, Sehitogulları A, Eren S, et al. The effect of metilprednisole on oleic-acid mediated acute respiratory distress syndrome. Türkiye Klinikleri J Med Sci 2003; 23:
23-6.
5. Yoshikawa S, Reynolds SD, Parker JC. Ventilator in- duced lung injury detected by plasma levels of Clara cell specific protein in mice. Am J Respir Crit Care Med 2003;
167: 775.
Table 1. Mann-Whitney U test was used for statistical comparison of control and IR groups.
Lung weight (mg)# % Lung weight loss Wet to dry ratio
Control IR p Control IR p Control IR p
Wet 776 ± 78 941 ± 90 0.009* --- --- --- --- --- ---
2ndh 296 ± 62 508 ± 35 0.002* 0.61 0.57 0.310 1.72 1.02 0.004*
4th h 157 ± 21 227 ± 49 0.041* 0.79 0.78 0.818 3.97 3.87 0.598
6thh 146 ± 20 183 ± 18 0.009* 0.80 0.80 0.394 4.32 4.13 0.394
12thh 146 ± 20 183 ± 18 0.009* 0.80 0.80 0.394 4.32 4.13 0.394
24thh 146 ± 20 183 ± 18 0.009* 0.80 0.80 0.394 4.32 4.13 0.394
2ndd 146 ± 20 183 ± 18 0.009* 0.80 0.80 0.394 4.32 4.13 0.394
3rdd 146 ± 20 183 ± 18 0.015* 0.80 0.80 0.394 4.32 4.13 0.394
4thd 146 ± 20 183 ± 18 0.015* 0.80 0.80 0.394 4.32 4.13 0.394
5thd 146 ± 20 183 ± 18 0.015* 0.80 0.80 0.394 4.32 4.13 0.394
7th d 146 ± 20 183 ± 18 0.015* 0.80 0.80 0.394 4.32 4.13 0.394
* Statistically significant.
# Mean ± standard deviation.
IR: Ischemia reperfusion.
